Zero fans is a nice idea but very difficult to implement, especialy if you overclock(why H2o if you don't???). The mosfets and ferite rings get VERY hot on my KX7 at default v~core(1.750volt), also in the PSU there's more than just the mosfets to cool, it was'nt included in the main PSU article last time I looked but BladeRunner at zerofan.com (or .co.uk ?) had to include a way of cooling the large ferrite ring in his H2o'd PSU it was getting above 60~70Deg IIRC...
It's much easier to have a bit of airflow in the case. I'd use out~of~case air ducted in through the radiator, then have it blowing onto the mobo and venting out through the case top. The air does'nt get noticably warmer unless you have a huge heatload like TEC's or multi+blocks
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Without airflow my mobo diode reaches temps of 33DegC+, with a small radial fan blowing across it does'nt go above 25DegC, if it was boxed up in a closed case it would get higher than 33DegC, probably nearer 40
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